The present invention relates to a device for filtering and separating flow media by reverse osmosis as well as by microfiltration, ultrafiltration, and nanofiltration with a pressure-tight housing having an inlet for the flow medium and an outlet for the retentate as well as for the permeate. A plurality of spacer elements are arranged within the housing whereby between two areal spacer elements, along which the flow medium passes, a filter element in the form of a membrane cushion is enclosed.
A device of the aforementioned kind is, for example, known from German Patent 37 15 183. In this known device the flow medium to be separated is introduced via an inlet of the device and passes in a controlled, regular pattern through the membrane cushions arranged between spacer elements so as to flow alternatingly from the exterior to the interior and from the interior to the exterior until it exits, after flowing past all of the membrane cushions, the device as an enriched retentate. The spacer elements are circular and the membrane cushions can also be of a circular design or, in approximation of a circular shape, may have the contour of a polygon.
With the known device very good results are achieved for certain applications such as sea water desalination, i.e., for producing portable water from sea water, whereby in the known device, even for large filter element stacks, the partial pressure differences of the flow medium between inlet and outlet remains within reasonable limits.
However, when flow media, for example, liquids with a high contents of organic and/or inorganic compounds must be separated, the rapid formation of a filter cake can disadvantageously be observed, because the compounds contained in the flow medium will deposit on the membrane cushions, respectively, at locations of the spacer elements at which the flow velocities of the flow medium is lower than at other locations of the device. This results in the device losing its separating capacity so that the device must be demounted and, if necessary, cleaned in a very complicated manner. This is especially disadvantageous in context with flow media of communal and/or industrial waste waters and highly loaded percolating water streams as, for example, occur at landfills. Such devices therefore are not suitable since, especially for the specified applications, the separating device must function essentially maintenance-free because an interruption of the function of the device for cleaning, maintenance, and replacement purposes would result in unacceptable ecological and economical consequences.
It is therefore an object of the present invention to provide a device of the aforementioned kind which is able, among other things, to separate liquids with a high organic and/or inorganic compound contents, for example, industrial and communal waste waters as well as highly loaded percolating water streams whereby no deposits in form of filter cakes should result during operation. Furthermore, the device, if this should become necessary, should allow for simple cleaning and maintenance and should provide for an inexpensive and simple manufacture. It should also be adaptable to individual loading degrees of the liquids to be separated.